Axonal damage probably occurs early in the evolution of MS. Five of 38 (13%) patients had a positive assay for the neuronal 14-3-3 protein in the CSF obtained at the first clinically isolated syndrome suggestive of MS. A positive 14-3-3 assay was the only independent predictor for a shorter time to conversion to clinical definite MS (risk ratio 4.1; 95% CI 1.1 to 15) and to reach an Expanded Disability Status Scale (EDSS) > or =2 at the end of follow-up (odds ratio 14.8; 95% CI 2.86 to 76.8). The detection of the 14-3-3 protein in the CSF at the first neurologic event suggestive of MS may be a useful predictor of short-term evolution.